Gyratory screening machine



R. A. DENOVAN GYRATORY SCREENING MACHINE April 5 1955 3 Sheets-Sheet 1 Filed Feb. 4, 1954 IHI April 5, 1955 R. A. DENOVAN 2,705551 GYRATORY SCREENING MACHINE Filed' Feb. 4, 1954 3 Sheets-Sheet 2 United States Patent GYRATORY SCREENING MACHINE Robert A. Denovan, Montreal, Quebec, Canada Application February 4, 1954, Serial No. 408,234 6 Claims. (Cl. 209 -332 This application relates to gyratory screening machines, and 1s a continuation-in-part of application, Serial No. 195,731, filed November 15, 1950, and now abanthe reaction at the discharge end is equal to the crosswise inertia force at the head end.

This combination of head-end forces makes it impossible to counterbalance the screen by means of a simple balance wheel. The best results possible is a compromise where the lengthwise forces are one-quarter under balanced and the crosswise forces one-quarter over balanced. No counterbalancing is feasible for the discharge end.

It is an object of the present invention to provide, in a gyrating screen having means for restraining movement of the discharge end thereof, improved driving means for imparting gyrating motion to the screen, such means being located directly below the body of the screen whereby more effective balancing and more efllcient screening action is obtained. A more specific object is to locate such driving means at substantially the center of percussion of the screen.

The invention will be described with reference to the accompanying drawing, in which Figure 1 is a side elevation, partly in section, of a screening machine in accordance with the invention,

Figure 2 is a plan view of the screening machine,

Figure 3 is an enlarged transverse sectional view of the screening machine,

Figure 4 is a plan view of a modified form of screening machine,

Figure 5 is a side elevation of the machine shown in Figure 4, and

Figure 6 is an enlarged sectional elevation of the driving means.

Referring to Figures 1 to 3, inclusive, 1 is the screen body proper which includes a substantially rectangular frame 2. The screen is mounted in inclined position and the lower or discharge end thereof is supported in suspended relation on the lower ends of a pair of rods 3 which are connected to the respective corners of the frame 2. The upper ends of the rods are connected to brackets 4 fixed to posts 5, the lower and upper ends of which are appropriately anchored to the floor and ceiling, as indicated at 6 and 7. Each end of the rods 3 is anchored in the bracket 4 or frame 2, as the case may be, by means of an annular rubber cushion 8, which permits limited swinging movement of the screen and rods.

The head end of the screen is supported on a drive head 9 mounted on a beam 10 extending transversely between two posts 11. The drive head comprises a driven shaft 12 which is substantially perpendicularly disposed with respect to the plane of the screen body and the axis of which may be located on the longitudinal axis of the screen body and spaced inwardly from the head of the body. Preferably, as shown, the drive is located substantially at the center of percussion of the screen. The shaft 12 is suitably supported on bearings 13 and 14 in housing 15 mounted on the beam 10. Fixed to the upper end of the shaft is a balance wheel 16, and extending above the balance wheel and also fixed to the upper end of the shaft is a bearing socket 17 formed by the cylindrical wall portion 18. The bearing socket 17 is off-center with respect to the shaft. By way of example, with a shaft of approximately 4" diameter and a balance wheel of about 38" diameter, the axis of the bearing socket may be offset from the axis of the shaft about 2".

An anti-friction bearing ring 19 is mounted in the socket in spaced relation to the bottom wall of the socket and is secured to the screen frame 2 by means of a selfaligning pivot block 20, which is fixed to and between a base plate 21, constituting the base of the screen body, and a transversely extending arch plate 22. The block 20 has an annular recess 20 into which extends the socket wall and bearing, as shown. The block 20 is connected to the bearing by means of a head pin 23 which extends axially through the housing and is fixed thereto by means of nuts 24 on the upper screw-threaded end thereof. The nuts are countersunk in the housing as shown, and a removable cover 25, with cap screw 26 is located in plate 21 to cover the opening. The head pin :23 has an annular groove 27 in its head to receive an annular flange 28 on a tapered sleeve 29 which extends between the block and bearing to lock the latter in proper running position. Such an arrangement makes the bearing readily releasable for dismantling. Thus, to release the same, the nuts 24 are removed and the pin 23 forced downwardly into the space at the bottom of the socket carrying with it the tapered sleeve, which thus frees the block from the hearing and permits the body of the screen to be lifted off.

The balance wheel 16 is provided with peripheral grooves 30 whereby it serves as a sheave driven by V- belts 31 from a motor 31 also mounted on beam 10.

The screen body shown comprises the lower base plate 21, which is perforated as shown and which is mounted on frame 2, and two superimposed spaced screening panels 33 and 34, divided into sections as shown and provided with cleaning balls 35. Screening panel 33 has a relatively coarse screen 36 and panel 34 has a finer screen 37. Each panel is covered with wire mesh 38. Three discharge chutes are provided, 39 for oversize material, 40 for middle size material, and 41 for fine size material.

Preferably, the discharge end of the screen is provided with a drag link 42, which is resiilently connected at one end through a pair of rubber washers 43 to a post 5 and at the other end through a pair of rubber washers 44 to the laterally opposite corner of the screen frame 2. This drag link tends toconstrain the movement of the discharge end of the screen to follow a virtually straight line forward and backward movement. One side of the head end of the screen body is also suspended from a rod 3 which is located laterally opposite the drive head and has its ends connected through annular rubber cushions 45 to a bracket 46 on a post 11 and to one end of the arch plate 22.

It will be observed that, except for the four supporting posts, the entire floor space beneath the screen is free which results in particularly convenient operation of the screen.

Referring to Figs. 4 and S, the modification therein illustrated is closely similar to that previously described. However, in this instance, the screen is self-supporting by providing braces 47 and 48 on the corner posts 5 and Moreover, instead of the single suspension rod 3, a second rod 49, laterally opposite the rod 3' and the drive center, is provided. Rod 49 is similarly connected through rubber washers 45 to a bracket 46 on the other post 11 and to the other end of arch plate 22.

In a gyratory screen, location of the drive within the screen body, i. e., directly below the screen body instead of at the end of the body, as is usual practice, has marked advantages in screening action and efficiency. Preferably, for maximum efficiency, the drive should be located at substantially the center of percussion.

In a screen body, the center of percussion is that point at which a suddenly applied force will cause rotation about the remote end, but with no other reaction. The center of percussion in a screen body, which is a rectangle of approximately uniform cross section, is

approximately on the longitudial axis about /3 of the length of the screen from the head end. As shown, the axis of the driven shaft 12 is located on the longitudinal axis of the screen body and about /3 of the length of the screen from the head end. Some slight deviation from this exact location is permissible without departing from the spirit of the invention While achieving the advantages thereof. Thus, a deviation of approximately 13 inches of the axis of shaft 12 on either side of the longitudinal axis of the screen body is permissible. For practical purposes, it is generally satisfactory if such deviation is made while maintaining the rim of the balance wheel 16 directly under the screen body.

With the drive so applied, the motion becomes circular at the drive point, elliptical at the head end, and, as before, takes place in a nominally straight line at the discharge end. The center of gravity moves the full diameter of the crank circle lengthwise and /3 of that distance crosswise, and the inertia forces are as great crosswise as lengthwise. Thus, the compromise counterbalancing becomes under lengthwise and /6 over" crosswise. Since inertia forces at the center of percussion are not transmitted to the remote end (discharge end), the latter end is nominally balanced. Thus, the unbalanced forces at the drive point are reduced from A to A5 and the reaction at the discharge end nominally eliminated (actually because of varying weight distribution some reaction is in evidence).

The functional advantages of the screen described are also important. Since the head end of the screen travels in a path of almost twice the length of travel of the discharge end, an intense screening action takes place in combination with a relatively mild action at the discharge end. This is particularly desired in processing of asbestos where intense screening action is desirable with a much milder action at the discharge end where the fibres are removed by a suction hood. The augmented swirling action resulting from the elliptical path at the head end, as compared with the ordinary circular path, also provides superior Stratification of the materials under treatment. I V

Since, except for the main drive bearing, all motion 18 substantially absorbed by the rubber cushions, the screen described is subject to a minimum of wear and maintenance costs.

While the screen mounting means may be varied within relatively wide limits, it will be observed that the means described results in a minimum of floor obstruction.

I claim: a

1. A screening device comprising a rectangular screening body having a base plate, a head end and a discharge end, means for suspending said body for gyratory screening motion above a floor surface and in inclined relation thereto with its head end in raised position with respect to its discharge end, said means comprising a supporting frame including a vertically disposed post adjacent each corner area of the body, a plurality of rigid rods, each having a resilient cushion at its upper end carried by one of said posts to suspend the rod therefrom, each rod also having a resilient cushion on its lower end connected to a respective one of the corner portions of the discharge end of the body and of the head end of the body, and a drive head engaging said body adjacent its head end to impart a rotary motion thereto and including a driven shaft mounted in the frame perpendicularly of and below said base plate, the axis of said shaft being in fixed relation to the frame, said axis of the shaft being within said body and located at a point substantially one-third of the length of the body from the head end, and crank means connecting the upper end of said shaft with said base plate.

2. A screening device comprising a rectangular screening body having a base plate, a head end and a discharge end, means for suspending said body for gyratory screening motion above a floor surface and in inclined relation thereto with its head end in raised position with respect to its discharge end, said means comprising a supporting frame including a vertically disposed post adjacent each corner area of the body, three rigid rods each having a resilient cushion at its upper end carried by one of said posts to suspend the rod therefrom, each rod also having a resilient cushion on its lower end connected to a respective one of the corner portions of the discharge end of the body and of the head end of the body, and a drive head engaging said body adjacent its head end to impart a rotary motion thereto and including a driven shaft mounted in the frame perpendicularly of and below said base plate, the axis of said shaft being in fixed relation to the frame, said axis of the shaft being within said body and substantially on the longitudinal axis of said body at a point substantially onethird of the length of the body from the head end, and crank means connecting the upper end of said shaft with said base plate.

3. A screening device as defined in claim 2, including a fourth one of said rigid rods having a resilient cushion on its upper end carried by the fourth one of said posts and a resilient cushion on its lower end connected to the body adjacent the head end thereof, said rods at the head end of the body being in substantially lateral alignment with said drive head.

4. A screening device as defined in claim 2, including a drag link resiliently connected to one of the corner portions of the discharge end of the body and to one of said posts adjacent the other corner portion of said discharge end.

5. A screening device comprising a rectangular screening body having a head end and a discharge end, means for suspending the body for gyratory screening motion including means for restraining movement of the discharge end, and means for imparting said motion including a driven shaft arranged substantially perpendicularly of said body and having its axis located within said body, and crank means connecting said shaft with the body, and comprising means forming a bearing socket fixed to and in axially offset relation to said shaft, a pivot block fixed to the screen body and having a portion extending axially into said socket, a bearing ring interposed between said portion and the socket wall, said portion being spaced from the bottom wall of the socket to provide a space therebetween, a pin extending axially through said portion and having a head located in said space, a tapered sleeve carried by said head and extending upwardly between said bearing ring and said portion, and means releasably holding said pin in fixed axial relationship to said portion to permit connecting and disconnection of said portion with said bearing ring.

6. A screening device comprising a rectangular screening body having a head end and a discharge end, means for suspending said body for gyratory screening motion above a floor surface and in inclined relation thereto with its head end in raised position with respect to its discharge end,said means comprising a supporting frame including a vertically disposed post adjacent each corner area of the body, four rods each having a resilient cushion at its upper end carried'by one of said posts to suspend the rod therefrom, each rod also having a resilient cushion on its lower end connected to a respective one of the corner portions of the discharge end of the body and of the head end of the body, and a drive head engaging said body adjacent its head end to impart a rotary motion thereto, said drive head comprising a driven shaft mounted in the frame substantially perpendicularly of said body, the axis of said shaft being in fixed relation to the frame, said axis of the shaft being within said body and intersecting the longitudinal axis of said body at a point substantially one-third of the length of the body from said head end, a balance wheel fixed to the upper end of the shaft, means forming a bearing socket on the upper end of the shaft above said balance wheel and located axially off-center from said shaft, a bearing ring in said socket, a self-aligning pivot block fixed to the screen body, means releasably connecting the pivot blltlackl to the bearing, and means for driving the balance w ee No references cited. 

